Pulse multiplex system employing fixed pulse-time displacement for signaling



Aprll 6, .1948, E. M. DELORAINE 2,438,902

' PULSE MULTIPLEX SYSTEM EMPLOYING FIXED PULSE-TIME DISPLACEMENT FOR SIGNALING Filed Oct. 4, 1945 yO/CE OU 7 PU 7- 1N VEN TOR'.

A TTaH/VEY @/G/ML Mmc/1776 Patented Apr. 6, 1948 PULSE MULTlI'LEX SYSTEM EMPLOYING FIXED PULSE-TIME DISPLACEMENT FOR SIGNALING Edmond M. Deloraine, New York, N. Y., assigner to Federal Telephone. and Radio Corporation, New York, N. Y., a corporation of Delaware Application October 4, 1943, Serial No. 504,881

In communication systems heretofore proposed,

Isuch as in telephone systems at present in use,

special signaling over the line often requires special equipment to be provided particularly at the terminals in order that the signals be transmitted over the voice frequency band without being interfered `With by voice currents, alternately signals are .transmitted below or above the voice frequency band and special equipment is required at the terminals to generate and receive the signal and at repeaters to by-pass and amplify these signals. Both systems involve a fairly large amount of equipment, expensive both in rst cost and maintenance cost.

It is an object of my invention therefore, to provide a simple type of signaling system particularly adapted for use with modulated impulse energy and requiring a minimum of terminal equipment to effect 4the desired signal control.

It is a further object of my invention to provide means for producing a signal interval in a train of impulses normally used for transmission of intelligence to provide the desired signaling.

It is a further object of my invention to alter the pulses of a time and/or amplitude modulated impulse channel to deiine a signaling interval therein.

A better understanding of my invention and the objects and features thereof may be had from the `particular description thereof, made withreference to the accompanying drawings, in which:

Fig. 1 illustrates a multiplex impulse communication system provided with signaling equipment in accordance with my invention;

Fig. 2 is a set of curves used in explaining the operation of the system of Fig. 1;

Fig. 3 is an illustration of a modified multiplex impulse transmission system using a different form of signaling in accordance with my invention; and

Fig. 4 is a curve used in explaining the operation of the system of Fig. 3,

Turning first to Fig. 1, a synchronizing source I is provided to synchronously control supervisory transmitter II and two other time modulated channels I2 and I3. Each of these transmission channels is of the type in which a train oi impulses is supplied, the impulses being modulated either in time or amplitude to convey intelligence over a transmission line, such as shown at I4. The synchronizing source serves to opers claims. (o1. 179;-15)

2 ate properly in timed relation the transmitters I I, I2 and I3 producing interleaved pairs of impulses I, 2 and 3, respectively, shown in Fig. 2. These impulses may be amplified in a repeater I5 which may be an ordinary pulse repeater. At the far end of line I4 the received pulses are applied to separate receivers I6, I'I and I8. These receivers are synchronized in operation from a synchronizing source I9, also coupled to line I4 so that the impulses of the corresponding channel, only, will be passed by the receiver for that channel. This synchronizing source may, for example, be of the type such Aas illustrated and described inthe copending application of applicant and N. H. Young, Jr., entitled Synchronizing circuit for multiplex pulse system," Serial No. 504,204, le'd September 29, 1943. Alternatively, the system may be any desired time pulse modulation system, iorexample, such as described in Patent No. 2,262,838, to E. M. Deloraine and A. I-I.` Reeves. In the output of each receiver is provided a line to the voice output circuits coupled over a condenser24 and a signaling circuit coupled over condenser 20. The particular type of impulse communication system is not material to the invention and so is not shown in detail.

When it is desired to transmit a signal, such as a ringing signal, the pulses of the selected channel are suppressed for a period providing the desired signaling interval. This may be accomplished, for example, by push buttons 25, 26 and 21. Depression of any of these push buttons disconnects the corresponding transmitter from line I4 so that the channel impulses are not transmitted during the period at which the button is depressed. Consider that push button 25 has been depressed, then impulses I shown in dotted line in Fig. 2 will be suppressed and will not appear on line I4. At receiver I6 a Wave such as shown at is provided to combine with the normally received impulses of this channel so as to select the desired channel impulses for demodulation. This serves to permit only impulses I to pass While blocking the receiver for impulses 2 and 3. As an example of a suitable circuit, reference is made tothe copending application of E. Labin and D. D. Grieg, Serial No. 488,183, led May 24, 1943, now Patent No. 2,419,570, dated April 29, 1947.

However, since during the signaling interval, the impulses from I I are suppressed, nothing will are applied from the output of receiver I6 over condenser 20 to the grid of vacuum tube 2 I. This energy maintains the tube in operation and energizes relay 22 which, in turn, serves to hold open its relay contacts 23. Upon cessation of signals, however, the tube 2I is no longer energized and permits relay 22 to release closing contacts 23. The closure of contacts 23 connects in circuit with a battery, a buzzer 29 which serves to produce the calling signal.

Similar circuit arrangements are provided the impulses by opening the circuit, known forms.

of combining circuits may be provided inthe tenis since it requires no special apparatus at the terminal stations or the repeaters to assure that the signaling energy is passed properly.

While the signaling energy has been described as a ringing frequency, it should be clear that signaling for any purpose such as for dialing, metering or other supervision may be accomplished in a similar manner, in accordance with my invention. Likewise, if desired, the direct current signaling of Fig. 3 may be applied simultaneously with the application of voice signals,

' the coupling condenser 24 in the voice line serving output of each transmitter to suppress the impulses.

In Figs. 3 and 4 is shown an alternative signaling arrangement in which, instead of suppressing the impulses, a fixed direct current, bia-s is given to the impulse producing device of a channel displacing the impulses by a fixed amount. In the present embodiment amplitude displacement is shown. Only transmitter II and receiver I6 are shown, the other transmitters and receivers being substantially duplicates of thi-s circuit. At the transmitting end is provided a battery 35 or other direct current source which, by closure of switch 36, is connected to transmitter I I serving to produce time displacement of the impulses transmitted from I I. These impulses are applied over line I and repeater I5 to the receiver I3 which may be the supervisory dernodulator circuit. Under normal conditions, when switch 35 is open, the output of receiver I3 will be an alternating current varying at voice or other intelligence frequencies as shown at 1I), Fig. 4.

When switch 36 is closed for signaling, voice frequencies generally will not be present and the output will be a substantially constant level direct current, as shown at 'Il of Fig. 4. Directly connected to the output of receiver demodulator I6 is a vacuum tube 3l and an input resistor 3B. Under normal intelligence transmission conditions, the output of receiver I6 will not cause' sufficient drop in resistor 30 to operate tube 3l. Upon arrival of a Vsignaling impulse, however, a

vrelatively strong constant D. C. will now through resistor 3U causing sucient drop therein to operate tube 3|. Tube 3l, upon operation, energizes relay 32 over a suitable time constant circuitA 33 closing contacts 3l and connecting buzzer 34 in series with its battery. Thus, during the signaling interval defined by impulse II, the buzzer will be operated.

It is clear that in place of a common direct current source such as shown in 35, a low frequency signaling source could be provided. In this case, however, a low'pass filter would be required in the output of receiver I6 to separate this low frequency signaling energy from the voice frequencies.

It is further clear that repeaters I5, shown in Figs. 1 and 3 may be of any type normally passing impulse modulations since the signaling condition applied to the line does not, in any way, alter the character of the impulses to be repeated.

It should be clear to those skilled vin the art also that ordinary ringing frequencies, such as 150 cycle energy, may be applied over the regular voice lines to lthe various transmitters to simply modulate the impulsesV in accordance with this lringing frequency. This system also-,presents to block the direct current from the voice outputs. However, in g-eneral, the signaling will take place at times when no voice is being transmitted. Accordingly, the system, such as shown in Fig. l, is readily applicable to these systems.

While I have described aboye the principles of my invention with references to other disclosuresV of specic apparatus, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects of my invention and the accompanying claims.

What is claimed is:

l. In an impulse transmission system wherein a train of impulses arranged in time spaced relation to one another and displaced in time from their normal positions in accordance with intellisence to be transmitted serves as a transmission carrier, a method of operating a signal controlled device over said carrier to indicate that a call is being made which comprises giving to said impulses a nxed modulating time displacement equivalent to a direct current impulse modulation to produce a modified signaling interval between discrete impulses of said train of impulseareceiving said train of impulses, and operating said signal controlled device in response to said modied signaling interval.

2. In an impulse transmission system wherein a train of impulses arranged in time spaced relation to one anotherV and displaced in time from their normal positions in accordance with intelligence to be transmitted serves as a transmission carrier, a method of operating a signal controlled device over said carrier to indicate that a call is being made which comprises modulating the impulses of said carrier with a signal producing time displacements of said impulses at a rate outside the frequency range of the transmitted intelligence to provide a modified signalling interval between discrete impulses of said train of impulses, receiving said train of impulses, and operating said signal controlled device in response to said modined signal interval.

3. A signaling system for transmitting control signals over an intelligence conveying channel carrier comprised essentially of a train of irnpulses spaced apartin time and adapted to be displaced in time from their normal positions in accordance with the amplitude of intelligence to be transmitted, comprising means for producing and transmitting said train of impulses, signal means for modulatingthe displacement of the impulses .ofsaid train to produce a fixed displacement thereof corresponding to said control-signals, receiver means for receiving said train of impulses, output means :for the intelligence conveyed by said impulse train, and signal controlled means in the output of said receiver means responsive to said fixed displacement for producing a signal.

4. A signaling system according to claim 5 wherein said signal controlled means comprises a relay circuit and means in said relay circuit for discriminating between control signals and said intelligence.

5. A signaling system for transmitting control signals over an intelligence conveying channel carrier compri-sed essentially of a train of impulses spaced apart in time and adapted to be displaced in time from their normal positions in accordance with the amplitude of intelligence to be transmitted, comprising means for producing and transmitting said train of impulses, signal means for impressing a direct current of predetermined amplitude on the means for producing said impulses for a predetermined period dening a modified signal interval between discrete impulses of said train corresponding to said control signals, said direct current producing a fixed displacement of said impulses, receiver means for receiving said train of impulses, a demodulator in -said receiver means for reproducing said intelligence and said direct current, and a signal controlled means comprising a relay means operative in response to said reproduced direct current.

6. In a, multi-channel transmission system wherein each channel of the system comprises a train of impulses displaced in time in accordance with the intelligence to be transmitted, the impulses of each channel being spaced in time with respect to one another to enable separation, a signaling system for operating a signal controlled device over any selected channel to indicate a call, comprising transmitter means for each channel to produce and transmit a train of impulses, signal means for operating on said selected trans mitter to produce a fixed displacement of the impulses from said selected transmitter, individual receivers for receiving said trains of impulses from the respective transmitters, signal responsive devices for each of said receivers, and means responsive to said xed displacement to operate said signal device at the selected receiver.

7. In a multi-channel transmission system wherein each channel of the system comprises a train of impulses displaced in time in accordance with the intelligence to be transmitted, the impulses of each channel being spaced in time with respect to one another to enable separation, a signaling system for operating a signal controlled device over any selected channel to indicate a call, comprising a direct current source, transmitter means for each channel to produce and transmit a, train of impulses, means for applying energy from said direct current source to said selected transmitter to effect a constant time displacement of the impulses to provide a modiiied interval between discrete impulses of said train of impulses from said selected transmitter, individual receivers for receiving and translating said trains of impulses from the respective transmitters to reproduce said direct current, signal responsive devices for each of said receivers, and means responsive to said reproduced direct current to operate said signal device at the selected receiver.

8. In an impulse transmission system wherein a train of impulses arranged in time spaced relation to one another and displaced in time from their normal positions in accordance with intelligence to be transmitted serves as a transmission carrier including an impulse modulator and means for applying intelligence amplitude signals to said modulator to produce corresponding time displacement of theimpulses; means for operating a signal control device over said carrier to indicate that a call is being made, comprising means for applying a direct current potential to said modulator to give to said impulses a xed modulating time displacement to produce a modined signalling interval between the received impulses of said train of impulses, mean-s for receiving said train of impulses, and means for operating said signal control device in response to said iixed modulating time displacement.

EDMOND M. DELO-RAINE.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS Number Name Date 2,262,838 Deloraine et al Nov. 18, 1941 2,048,081 Riggs July 21, 1936 2,263,369 Skillman Nov. 18, 1941 1,711,651 Pruden May 7, 1929 525,703 Gilliland Sept. 11, 1894 1,485,773 Espen-schied Mar. 4, 1924 1,976,096 Ryall Oct. 9, 1934 2,326,584 Van Zeist Aug. 10, 1943 1,452,925 Nottage et al Apr. 24, 1923 1,464,104 Nicholson Aug.` 7, 1923 1,205,460 Lyons Nov. 21, 1916 1,804,526 Coxhead May 12, 1931 Number Country Date 536,963 Great Britain June 3, 1941 418,525 Great Britain Oct. 26, 1934 

